Buggy code:
public final class CompletionEngine extends Engine implements ISearchRequestor , RelevanceConstants , TypeConstants , TerminalTokens { public static boolean DEBUG = false ; private static final char [ ] ERROR_PATTERN = "*error*" . toCharArray ( ) ; private static final char [ ] EXCEPTION_PATTERN = "*exception*" . toCharArray ( ) ; private static final char [ ] SEMICOLON = new char [ ] { ';' } ; private static final int SUPERTYPE = 1 ; private static final int SUBTYPE = 2 ; private static final int FIELD = 0 ; private static final int LOCAL = 1 ; private static final int ARGUMENT = 2 ; int expectedTypesPtr = - 1 ; TypeBinding [ ] expectedTypes = new TypeBinding [ 1 ] ; int expectedTypesFilter ; int uninterestingBindingsPtr = - 1 ; Binding [ ] uninterestingBindings = new Binding [ 1 ] ; boolean assistNodeIsClass ; boolean assistNodeIsException ; boolean assistNodeIsInterface ; IJavaProject javaProject ; CompletionParser parser ; ICompletionRequestor requestor ; ProblemReporter problemReporter ; char [ ] source ; char [ ] token ; boolean resolvingImports = false ; boolean insideQualifiedReference = false ; int startPosition ; int actualCompletionPosition ; int endPosition ; int offset ; HashtableOfObject knownPkgs = new HashtableOfObject ( 10 ) ; HashtableOfObject knownTypes = new HashtableOfObject ( 10 ) ; Scanner nameScanner ; static final char [ ] [ ] baseTypes = new char [ ] [ ] { "boolean" . toCharArray ( ) , "byte" . toCharArray ( ) , "char" . toCharArray ( ) , "double" . toCharArray ( ) , "float" . toCharArray ( ) , "int" . toCharArray ( ) , "long" . toCharArray ( ) , "short" . toCharArray ( ) , "void" . toCharArray ( ) } ; static final char [ ] classField = "class" . toCharArray ( ) ; static final char [ ] lengthField = "length" . toCharArray ( ) ; static final char [ ] THIS = "this" . toCharArray ( ) ; static final char [ ] THROWS = "throws" . toCharArray ( ) ; static InvocationSite FakeInvocationSite = new InvocationSite ( ) { public boolean isSuperAccess ( ) { } public boolean isTypeAccess ( ) { } public void setActualReceiverType ( ReferenceBinding receiverType ) { } public void setDepth ( int depth ) { } public void setFieldIndex ( int depth ) { } } ; public CompletionEngine ( ISearchableNameEnvironment nameEnvironment , ICompletionRequestor requestor , Map settings , IJavaProject javaProject ) { } public void acceptClass ( char [ ] packageName , char [ ] className , int modifiers ) { } public void acceptInterface ( char [ ] packageName , char [ ] interfaceName , int modifiers ) { } public void acceptPackage ( char [ ] packageName ) { } public void acceptType ( char [ ] packageName , char [ ] typeName ) { } private void complete ( AstNode astNode , AstNode astNodeParent , Binding qualifiedBinding , Scope scope ) { } public void complete ( IType type , char [ ] snippet , int position , char [ ] [ ] localVariableTypeNames , char [ ] [ ] localVariableNames , int [ ] localVariableModifiers , boolean isStatic ) { IType topLevelType = type ; while ( ( topLevelType . getDeclaringType ( ) ) != null ) { topLevelType = topLevelType . getDeclaringType ( ) ; } CompilationResult compilationResult = new CompilationResult ( ( ( topLevelType . getElementName ( ) ) + ".java" ) . toCharArray ( ) , 1 , 1 , this . compilerOptions . maxProblemsPerUnit ) ; CompilationUnitDeclaration compilationUnit = new CompilationUnitDeclaration ( problemReporter , compilationResult , 0 ) ; try { <START_BUG> TypeDeclaration typeDeclaration = TypeConverter . buildTypeDeclaration ( type , compilationUnit , compilationResult , problemReporter ) ; <END_BUG> if ( typeDeclaration != null ) { Initializer fakeInitializer = parseSnippeInitializer ( snippet , position , localVariableTypeNames , localVariableNames , localVariableModifiers , isStatic ) ; FieldDeclaration [ ] oldFields = typeDeclaration . fields ; FieldDeclaration [ ] newFields = new FieldDeclaration [ ( oldFields . length ) + 1 ] ; System . arraycopy ( oldFields , 0 , newFields , 0 , oldFields . length ) ; newFields [ oldFields . length ] = fakeInitializer ; typeDeclaration . fields = newFields ; if ( CompletionEngine . DEBUG ) { System . out . println ( "SNIPPET<seq2seq4repair_space>COMPLETION<seq2seq4repair_space>AST<seq2seq4repair_space>:" ) ; System . out . println ( compilationUnit . toString ( ) ) ; } if ( ( compilationUnit . types ) != null ) { try { lookupEnvironment . buildTypeBindings ( compilationUnit ) ; if ( ( unitScope = compilationUnit . scope ) != null ) { lookupEnvironment . completeTypeBindings ( compilationUnit , true ) ; compilationUnit . scope . faultInTypes ( ) ; compilationUnit . resolve ( ) ; } } catch ( CompletionNodeFound e ) { if ( ( e . astNode ) != null ) { complete ( e . astNode , parser . assistNodeParent , e . qualifiedBinding , e . scope ) ; } } } } } catch ( JavaModelException e ) { } } private Initializer parseSnippeInitializer ( char [ ] snippet , int position , char [ ] [ ] localVariableTypeNames , char [ ] [ ] localVariableNames , int [ ] localVariableModifiers , boolean isStatic ) { } public void complete ( ICompilationUnit sourceUnit , int completionPosition , int offset ) { } private TypeBinding [ ] computeTypes ( Expression [ ] arguments , BlockScope scope ) { } private void findAnonymousType ( ReferenceBinding currentType , TypeBinding [ ] argTypes , Scope scope , InvocationSite invocationSite ) { } private void findClassField ( char [ ] token , TypeBinding receiverType , Scope scope ) { } private void findExplicitConstructors ( char [ ] name , ReferenceBinding currentType , MethodScope scope , InvocationSite invocationSite ) { } private void findConstructors ( ReferenceBinding currentType , TypeBinding [ ] argTypes , Scope scope , InvocationSite invocationSite , boolean forAnonymousType ) { }

Fix:
TypeDeclaration typeDeclaration = TypeConverter . buildTypeDeclaration ( type , compilationUnit , compilationResult ) ;